Chamfer

A chamfer /ˈʃæm.fər/ is a transitional edge between two faces of an object. It can also be known as a bevel but connotes more often cutting and is more often 45° with respect to the two adjoining faces. If the un-chamfered intersection of the adjoining faces would otherwise form a right angle, 90° as is most common, the chamfer will typically be uniform and pitched at 45° . A fully chamfered square interior would thus be octagonal. (By contrast, a fillet is the rounding-off of an interior corner, and a rounding of an exterior corner is called a "round" or a "radius")

"Chamfer" is a term commonly used in mechanical and manufacturing engineering. Special tools such as chamfer mills and chamfer planes are available. In tile work, or furniture such as counters or table tops, an edge or arris that has been eased by rounding instead of chamfering is called a bullnose. Where a chamfer does not go to the end of the piece, but "lifts out" in a smooth curve, the end is called a lark's tongue.

In non-aesthetic uses, chamfers are necessary in parabolic glass mirror manufacture and desirable in certain printed circuit boards. A chamfer is also often used to make an otherwise sharp edge safer when a machined metal part is intended to be handled by a person.

In architecture, the base of the Taj Mahal is a cube with chamfered corners, thereby creating an octagonal architectural footprint. Its great gate is formed of chamfered base stones and chamfered corbels for a balcony or equivalent cornice towards the roof.

...
Wikipedia